In a blog post, the director of Google’s self-driving car program described all the accidents as minor, with no injuries, over 1.7 million miles of driving. “Light damange, no injuries,” wrote Chris Urmson. Accidents occurred in the cars both when the car was driving itself and when it was being driven in a normal manner by a worker behind the wheel.

Urmson’s post came the same day as the Associated Press reported four self-driving cars have been involved in accidents in California since September. Three of the crashes involved cars being operated by Google, which has a fleet of 23 self-driving Lexuses, the source said. The other is owned by Delphi, a big auto industry supplier.

In two of the four cases, the car was doing the driving at the time of the crash, the AP says, based on an unnamed source. In the other two, the person behind the wheel had taken control of the car. The crashes were among the nearly 50 self-driving cars now being operated in the Golden State.

Delphi also told the AP that its crash was minor, that it was not at fault and released a copy of an accident report..

California’s motor vehicles department confirmed four crashes had occurred, but would not indicate blame or other details citing confidentiality laws.